The invention relates to a pre-filled hypodermic syringe fitted with a stoppering device.
Pre-filled syringes are provided in the form of a standard syringe whose outlet end has a tip fitted with a removable stopper which is mounted sealingly thereon.
FIG. 1 shows such a pre-filled hypodermic syringe. The latter comprises a tubular body 1 with a generally cylindrical shape. This tubular body has a first open end 2.
A plunger 6 passes through the opening of the first end 2 of the tubular body 1. At its end mounted in the tubular body 1, the plunger 6 has a piston 4 which is able to slide inside the tubular body 1 in the longitudinal direction thereof. The plunger 6 thus allows the user to move the piston in translation.
The outer surface of the tubular body 1 has a flange 7 at the first end 2. The user's fingers are placed on the flange, and the piston 4 can be actuated by pressing on the end of the plunger 6 remote from the end connected to the piston 4.
The second end 3 of the tubular body has a wall 8 that is substantially transverse and open at its center.
The tubular body 1 additionally has a connection tip 9 of the Luer lock type arranged at its second end 3, on the outer face of the wall 8. As is known per se, the tip 9 is composed of a tubular part 10 and of a threaded part 11 forming a neck.
The tubular part 10 is of substantially conical shape, and the opening situated at the end of greater diameter of the tip is coincident with the opening of the wall 8.
The threaded part 11 of the tip is intended to allow a tip of complementary shape to be screwed on, allowing a needle or infusion line to be connected to the syringe. The threaded part 11 is arranged coaxially with respect to the tubular part 10 and outside of the latter.
A stopper 12 is screwed onto the tip 9, by means of the threaded part 11, thereby covering the opening of the tubular part 10 of the tip 9.
The tubular body 1, the piston 4, the wall 8, the tubular part 10 of the tip 9, and the stopper 12 thus delimit a leaktight space serving as a reservoir for a fluid that is to be administered to a patient.
The stopper 12 closing off the tubular part 10 of the tip 9 can be removed by unscrewing it. Once the needle or infusion line has been connected to the tip 9, the plunger 6 allows the operator to actuate the piston 4 and thus administer to the patient the fluid contained in the reservoir.
The advantage of a pre-filled syringe is that it avoids the user transferring a medicament from any given container into the syringe prior to use. These syringes generally have a gradation that permits the desired dosing.
The pre-filled syringe is packaged in a blister pack closed off by a cover made of peel-off paper. This paper has the particular feature of being permeable to water vapor but impermeable to microorganisms. The whole assembly is sterilized with wet heat, that is to say by the parts to be sterilized coming into contact with high-temperature vapor. This vapor originates from a chamber of an autoclave, passes through the peel-off cover and thus reaches the various parts of the syringe that are to be sterilized.
However, since the removable stopper is mounted in a leaktight manner on the tip, the zone situated between these two elements is not accessible to the vapor. The outer face of the tip cannot therefore be sterilized using the wet heat sterilization method.
The whole assembly therefore has to be sterilized with dry heat in such a way as to guarantee sterility between the stopper and the tip on which it is mounted.
This method requires a longer sterilization time than does sterilization with wet heat.
The longer sterilization time increases the cost of producing such a syringe. It also causes greater degradation of the plastic material of the body of the pre-filled syringe, thereby increasing the risk of products of degradation being released into the solution. In addition, the prolonged exposure to high temperatures causes unacceptable degradation of certain active principles.
A further problem arises from the syringe being closed by a stopper.
When a stopper made of plastic material, generally polypropylene, is used, it is normally screwed onto a tip of the Luer lock type.
Regardless of the tightening torque at the moment when the stopper is screwed onto the tip, a relaxation of the tightening is observed during sterilization. This relaxation is caused by softening of the polypropylene at high temperature, and this compromises the leaktightness between the stopper and the tip.
In the case where a stopper made of elastomer is mounted by elastic clamping on the tip, the stopper is not affected by the rise in temperature. However, the sterilization creates an adherence of the stopper to the tip, making it difficult for the user to remove the stopper.
Document US 2005/0283116 describes a pre-filled hypodermic syringe comprising:                a tubular body having two open ends and containing a fluid to be administered to a patient,        a plunger which, at one of its ends, has a piston mounted slidably in the tubular body and which passes through the opening of the first end of the tubular body,        a connection tip in the form of a cone of the Luer or Luer-lock type, for example for connection to a needle or infusion line, which connection tip is intended for passage of the fluid to be administered and comprises a tubular part communicating with the opening of the second end,        the tip comprising an obturator connected by a frangible zone to the free end of its tubular part,        the syringe being made of synthetic material and produced by molding, the obturator being molded in one piece with the tip and the tubular body, the syringe comprising a cap mounted on the tip.        
The syringe is produced by molding, the outer forms of the syringe being delimited in a conventional manner by the walls of a mold, a core delimiting the inner volume of the tubular body and of the tubular part of the tip. In order to compensate for the dimension tolerances and for the deviations in the positioning of the core in the mold, the frangible zone formed at the end of the tubular part of the tip must necessarily have a sufficient thickness to ensure continuity of the material, even in the event of a fault in the positioning of the core.
The obturator is withdrawn by tilting it sideways with the aid of a cap provided with a slit.
In this case, the frangible zone connecting the obturator to the tip is subjected to heterogeneous stresses, namely tensile stresses on the one hand and compression stresses on the other. The poor distribution of the stresses in the frangible zone makes it uncertain that the frangible zone will be broken completely by a single tilting movement, which generally forces the user to perform an alternative movement. The presence of a thickness of material at the level of the frangible zone makes it all the more difficult to cleanly separate the obturator and the tip.
If a clean break is not obtained, particles may be produced when the tip is torn off, such that the solution contained in the syringe is contaminated.
The present invention therefore seeks to overcome these disadvantages by making available a syringe which can be sterilized easily and without extra expense and whose content is not affected by the sterilization, and which provides complete leaktightness while at the same time allowing the obturator and the tip to be separated efficiently.